In the repair of gas turbine engine high temperature operating components, such as high pressure turbine vanes which have been operated at high temperatures in an engine, it has been a practice first to clean the component to remove surface contaminants such as oxides at or within a surface discontinuity such as a crack, crevice, surface abrasion or wear area, etc. One commonly used cleaning method sometimes is referred to as Activated Diffusion Healing (ADH) and generally is described in U.S. Pat. No. 4,098,450--Keller et al, patented Jul. 4, 1978, the disclosure of which hereby is incorporated herein by reference. In that method, the component's surface discontinuity, such as a crack, is exposed to fluoride ions which convert oxides present to a gas which then leaves the surface portion to be repaired. In this way, the surface portion is cleaned and prepared for repair.
Repair of a Co base superalloy turbine vane made of an alloy sometimes referred to as X-40 alloy has included the above described fluoride ion cleaning method followed by a vacuum heat treatment, repair alloy application to the cleaned surface portion, and a diffusion heat treatment. The composition of the X-40 alloy includes, by weight, about: 0.45-0.55% C, 24.5-26.5% Cr, 7-8% W, 9.5-11.5% Ni, with the balance Co and incidental impurities, such as Mn, Si, S, and Fe at levels which do not adversely affect the function of the alloy. It has been observed that sometimes cracks can occur in a part of the component, such as the outer band carrying the vanes or in the vane itself or both, after such repair procedure. Application of a second round of the ADH process to repair the crack can add as much as a week or more to the repair cycle of a component, thereby dramatically increasing repair costs. On the other hand, welding can be accomplished in a few hours. Therefore, because X-40 alloy has been considered in the past to be a readily weldable alloy, cracks in the component, such as the outer band, have been repaired by welding with a welding wire made of one of a number of alloys. One frequently used welding wire is made from an alloy sometimes referred to as L-605 alloy and consisting nominally, by weight, of about: 10% Ni, 3% Fe, 20% Cr, 1% Si, 15% W, 1.5% Mn, with the balance Co and incidental impurities. A repetitive weld cycle sometimes is entered into in which the welding leads to additional cracking. Occasionally, the component being repaired is so distorted by welding that it must be scrapped. Also, when the component includes a cooling hole through a surface of the article and a discontinuity such as a crack exists in the hole's vicinity, such as at or near such hole, welding to repair the crack can be difficult in such vicinity, occasionally generating additional cracks.